Monday’s deadly shooting at Washington’s Navy Yard led to uneven security measures across the Capitol complex as armored vehicles rolled around the East Front of the Capitol and Capitol Police officers donned enhanced tactical gear. But the two chambers went in different directions regarding protocol for staff and members, and the Capitol Visitor Center continued to give tours up until closing time at 4:30 p.m.

The Senate recessed shortly after convening at 2 p.m. Monday, and Senate Sergeant-at-Arms Terrance Gainer gave Senate employees a shelter-in-place order about an hour later.

The House, meanwhile, convened for a brief pro forma session at 2 p.m. and recessed, but it did not give any order to shelter in place or lock down the chamber.

Shortly before the House pro forma session, at 1:30 p.m., House Sergeant-at-Arms Paul Irving sent an email to House staff.

“The facts available from the shootings at the Navy Yard continue to evolve,” he wrote. “Information about additional shooters is yet unclear, and not confirmed. We are evaluating available intelligence and evidence. There is no information indicating the Capitol Complex, staff, visitors or Members are at risk. The USCP has implemented substantial additional security measures. We will keep you apprised of information,” Irving’s notice stated.

Gainer’s notice, which went out at 3:12 p.m. stated: “In light of the uncertainty surrounding the shooting at the Navy Yard this morning and particularly the possibility of suspects remaining at large, we have decided to lock down the Senate complex. You may move about the building; however, for the next two hours you may not leave nor can anyone enter the building. This will be in effect until we deem the situation safe in the neighboring community.”

The result, at least for a few hours, was that no one could leave the Senate chamber, unless, of course, they walked across the Rotunda to the House. A group of six Capitol Police officers stood on the Senate side of the Rotunda during the lockdown, warning anyone who approached that if they crossed out of the Senate side of the Capitol, they would not be allowed to return.

The Capitol Visitor Center was never locked down. “We did not shut down during the lockdown, and we were still receiving visitors right up to our 4:30 p.m. closing time. The lockdown had no impact on our tours,” Tom Fontana, director of communications for the CVC, told CQ Roll Call.

“It’s been business as usual up here. Other than the increased Capitol Police presence and security being pretty tight, nothing has changed,” Senate Periodical Press Gallery Director Ed Pesce said shortly before the lockdown order was issued.

With at least 13 confirmed dead and law enforcement still chasing leads on the motive behind the attacks, as well as how many attackers were involved, Gainer said he was taking no chances, particularly in light of other mass shootings over the past few years.

“I delayed the lockdown while gathering facts. At first this looked like a lone shooter, all the earmarks of some type of workplace violence or isolated vengeance. The reasons for the different approaches by the House and Senate sergeant-at-arms are varied, but in the end [were] judgment calls. My decision was based on participating in reviews of shootings at Sandy Hook, Columbine, Virginia Tech and Aurora, Colo., as well as the bombings in Boston. I have spent considerable time with the heads of those agencies. We had direct discussions with [D.C. Metropolitan Police Chief Cathy Lanier.] I elected to err on the side of caution. The only harm was inconvenience to staff, members and visitors. I hope this helps,” Gainer told CQ Roll Call.

Gainer partially lifted the lockdown shortly after 4 p.m.

Still, the dissonance between House and Senate procedures, as well as the delay in the lockdown, made for a confusing afternoon.

For one, even though Gainer sent earlier email updates on the shooting to staff, his order to shelter in place was not communicated until several hours after the shooting occurred.

For another, the enhanced security posture of the Capitol Police signaled that precautions were being taken, even as the House side did not restrict visitor access or recommend a shelter-in-place and the CVC continued to show tourists around.

Asked whether screening procedures would change at Capitol building entrances, Antrobus said he was not aware of anything specific, but he added, “I think the thing is we’ve always been very, very careful when we screen individuals, so we’re continuing our strict security.”